<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Returns the first value from a queue</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="class.pht-queue.html">pht\Queue</a></div> <div class="next" style="text-align: right; float: right;"><a href="pht-queue.lock.html">pht\Queue::lock</a></div> <div class="up"><a href="class.pht-queue.html">pht\Queue</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="pht-queue.front" class="refentry"> <div class="refnamediv"> <h1 class="refname">pht\Queue::front</h1> <p class="verinfo">(PECL pht >= 0.0.1)</p><p class="refpurpose"><span class="refname">pht\Queue::front</span> — <span class="dc-title">Returns the first value from a queue</span></p> </div> <div class="refsect1 description" id="refsect1-pht-queue.front-description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="modifier">public</span> <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><strong>pht\Queue::front</strong></span> ( <span class="methodparam">void</span> )</div> <p class="para rdfs-comment"> This method will remove a value from the front of the queue (in constant time). Attempting to return the front value from an empty queue will result in an <a href="class.error.html" class="classname">Error</a> exception. </p> <div class="caution"><strong class="caution">Caution</strong> <p class="para"> Due to the fact that all values in a <a href="class.pht-queue.html" class="classname">pht\Queue</a> are serialised, extracting a value from the queue will require it to be deserialised. This can incur a noticeable performance hit if the inspection of the queue's front value is performed within a loop. </p> </div> </div> <div class="refsect1 parameters" id="refsect1-pht-queue.front-parameters"> <h3 class="title">Parameters</h3> <p class="para">This function has no parameters.</p> </div> <div class="refsect1 returnvalues" id="refsect1-pht-queue.front-returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> The value on the front of the queue. </p> </div> <div class="refsect1 examples" id="refsect1-pht-queue.front-examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example" id="example-4567"> <p><strong>Example #1 Retrieving the front value of a queue</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">use </span><span style="color: #0000BB">pht</span><span style="color: #007700">\</span><span style="color: #0000BB">Queue</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$queue </span><span style="color: #007700">= new </span><span style="color: #0000BB">Queue</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">push</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">front</span><span style="color: #007700">());</span> </span> </code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents screen"> <div class="cdata"><pre> int(1) </pre></div> </div> </div> </p> <p class="para"> <div class="example" id="example-4568"> <p><strong>Example #2 Retrieving the front value in a loop (bad example - don't do this)</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">use </span><span style="color: #0000BB">pht</span><span style="color: #007700">\</span><span style="color: #0000BB">Queue</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$queue </span><span style="color: #007700">= new </span><span style="color: #0000BB">Queue</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">push</span><span style="color: #007700">(</span><span style="color: #0000BB">array_fill</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">2000</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">));<br /><br />for (</span><span style="color: #0000BB">$i </span><span style="color: #007700">= </span><span style="color: #0000BB">0</span><span style="color: #007700">; </span><span style="color: #0000BB">$i </span><span style="color: #007700">< </span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">front</span><span style="color: #007700">()); ++</span><span style="color: #0000BB">$i</span><span style="color: #007700">); </span><span style="color: #FF8000">// quadratic runtime</span> </span> </code></div> </div> </div> </p> <p class="para"> <div class="example" id="example-4569"> <p><strong>Example #3 Retrieving the front value in a loop (good example)</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">use </span><span style="color: #0000BB">pht</span><span style="color: #007700">\</span><span style="color: #0000BB">Queue</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$queue </span><span style="color: #007700">= new </span><span style="color: #0000BB">Queue</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">push</span><span style="color: #007700">(</span><span style="color: #0000BB">array_fill</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">2000</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">$front </span><span style="color: #007700">= </span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">front</span><span style="color: #007700">(); </span><span style="color: #FF8000">// create a separate variable<br /></span><span style="color: #007700">for (</span><span style="color: #0000BB">$i </span><span style="color: #007700">= </span><span style="color: #0000BB">0</span><span style="color: #007700">; </span><span style="color: #0000BB">$i </span><span style="color: #007700">< </span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$front</span><span style="color: #007700">); ++</span><span style="color: #0000BB">$i</span><span style="color: #007700">); </span><span style="color: #FF8000">// linear runtime</span> </span> </code></div> </div> </div> </p> </div> </div><hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="class.pht-queue.html">pht\Queue</a></div> <div class="next" style="text-align: right; float: right;"><a href="pht-queue.lock.html">pht\Queue::lock</a></div> <div class="up"><a href="class.pht-queue.html">pht\Queue</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div></body></html>